Control system



Oct. ll, 1949. E. B. FxTzGERALD CONTROL SYSTEM.

2 SheetsSheet 1 INVENTOR {dn/0rd,@ /WZyQra/d ATTO EY Uil Filed Aug. 18, 1945 Oct. ll, 1949.

EQ B. FITZGERALD CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Aug. 18, 1945 INVENTOR {diva/"075 f zyfrab d la D ATTO f NEY Patented Oct. 11, 1949 CONTROL SYSTEM Edward B. Fitzgerald, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 18, 1945, Serial No. 611,398

(Cl. S18-380) Claims. l

My invention relates, generally, to control systems and, more particularly, to systems for controlling the operation of electrically propelled vehicles, such as trolley coaches.

On vehicles which are equipped only with straight air brake apparatus, a broken air line, with a corresponding loss of air pressure, leaves the operator dependent on the hand brake for stopping the vehicle. Furthermore, in the case of a trolley coach equipped with pneumatically operated control apparatus loss of air pressure also prevents the operation of the dynamic electric braking equipment.

An object of my invention is to provide for automatically bringing a vehicle under control before complete loss of air pressure from the pneumatically operated control apparatus.

Another object of my invention is to provide for automatically cutting oif power from the propelling motor of a vehicle and establishing dynamic braking connections for the motor when the air pressure drops below a predetermined amount.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of my invention, a pneumatically operated pressure relay is utilized to warn the operator of a vehicle, cut orf power from the propelling motor and establish dynamic braking connections for the motor independently of the position of the master controller when the pressure in the air supply system drops below a predetermined amount.

For a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of a control system embodying my invention;

Fig. 2 is a schematic diagram of the main circuit-s shown in Fig. 1; and

Figs. 3, 4 and 5 are charts showing the sequence of operation of the apparatus illustrated in Figs. 1 and 2.

Referring to the drawings, and particularly to Fig. 1, the system shown therein comprises a traction motor TM having an armature winding I0 and a series eld winding II; a line switch LS for connecting the motor TM to a power conductor I2 which may be energized from a trolley conductor I3 through a current collecting device I4; a plurality of reversing switches FI, F2, Rl and R2 for controlling the direction of operation of the motor TM and also connecting the motor to a power conductor I5 which is connected to a trolley conductor I6 through a current collecting device il; a switch B which cooperates with certain of the reversing switches to establish dynamic braking connections for the motor TM as described in detail in the copending application of L. G. Riley, Serial No. 508,265, filed. October' 29, 1943, Patent No. 2,455,892, issued December 12, 1948; and a switch E which connects the field winding Il of the motor TM to the power conductor l2, thereby exciting the motor field during dynamic braking. A resistor I8 is connected in the excitation circuit for the field winding II and a resistor I9 is connected in the dynamic braking circuit for the motor TM.

The motor current is controlled both during acceleration and dynamic braking by a resistor R which is shunted from the motor circuit stepby-step by a controlled CC which is provided with a plurality of contact members I to 8 inclusive, for shunting the resistor -R. The controller CC may be of the cam or the drum type having a shaft 2l which is driven by an air engine 22 of a type well known in the art.

The air engine 22 is provided with a standard magnet valve SV and an inverted magnet valve IV. The operation of the air engine is automatically controlled during both acceleration and dynamic braking by a current limit relay LR having a series coil 23 which is connected in the motor circuit and is, therefore, responsive to the motor current during both acceleration and dynamic braking. The series coil 23 is divided into two sections, only one of which is utilized during acceleration and both `of which are utilized during dynamic braking, thereby changing the calibration of the relay LR during braking.

In order to provide for changing the calibration of the limit relay LR still further during dynamic braking to prevent the maximum permissible voltage for the motor from being exceeded when the Vehicle is operating at high speeds, the relay LR is also provided with a shunt coil 24. As shown and claimed in the copending application of S. E. Newhouse, Serial No. 589,474, filed April 21, 1945, Patent 2,479,397, issued August 16, 1949, the shunt coil 24 is connected across two steps of the resistor R through a resistor 25 and contact members 26 on the line switch LS and 21 on the controller CC. These are the first two steps which are shuntedfrom the motor circuit during dynamic braking. It will be understood that the coil 24 may be connected across one or more additional steps of the resistor R if desired.

Manually operable controllers CS and MC are provided for controlling the operation of the reversing switches and the line switch LS, and for controlling the supply of control current to the air engine 22. The controller MC controls the operation of the control apparatus during acceleration, and a controller BC controls the operation of the apparatus during dynamic braking. The controllers MC and BC are interlocked in the usual manner to prevent improper operation of the equipment in the event that both of the controllers are operated simultaneously.

With a View to disconnecting the motor TM from the power source and automatically establishing the dynamic braking circuit for the motor in the event that the pressure "in the air supply system decreases below a certain amount, an air pressure relay PR is provided. As shown, the relay PR comprises a piston 28 disposed in a cylinder 29. The cylinder 29 is so connected to the air supply 'system that the piston "28 is forced upwardly against a spring 3U, thereby yclosing certain contact members of the relay and yopening other contact members so long as the pressure in the air supply system is maintained above a certain amount.

When the pressure in the system is lowered, the piston 2'8 is actuated downWa-rdly'to-open certain of the contact members vand -close the other contact members. As shown, the -contact members which are lclosed when the piston is actuated upwardly by the yair pressure may be slidably mounted -on the stem of the relay and biased upwardly 'by springs disposed 'on the relay stem. These contact members may be so mounted on the relay stem that they open a short time prior to the closing -of the other lcontact members, as the piston `28 moves downwardly.

The contact members of the relay VPR are so connected lin the control system that the motor TM is rst disconnected from the vpower source `and the dynamic braking circuits then established when the air pressureall's 4below a predetermined amount, An -al'arm A, `which 'is energized through a circuit-established by one of the contact members of the relay :is provided to warn the operator -of the Ydecrease 'in the pressure in the air supplysystem.

In order that the 'functioning of the v-ioregoing apparatus may Vbe more clearly understood, the operation of the system rwill now be described in more detail. Assuming that itis desired to accelerate the vehicle in 'a forward ldirection, the control switch CS is 'actuated '-to the 'forward position and the controller MC is actuated to posi- -tion il. At this time, an energizing :circuit is established for the 'actuating coil A'of the line switch LS, which may -be traced from positive through a Vcontact segment 3l on the control switch CS, conductor 312, a segment 33 1on the controller MC, conductor 34, 'a segment 35 on the controller BC, 'conductor 36, 'contact 'members '2B on 'the relay 13R-conductor '3-1, an interlock 38 on the switch B, vconductor 35, vthe actuating coil ofthe switch LS,con"ductor"40, and-contact members 4I, -4'2 and '43 on the lcontroller "CC to negative. A holding circuit `is established for the line switch LS 'through an 'interlock I4 on the switch LS.

At this time, the reversing switches 'F'I `'and F2 are 'also closed. The energizing circuit for the switch 'Fl l'extends Afrom positive -through a vcontact segment A45 on the 'switch CS, conductor 46, a segment "41 'on fthe 'switch MC, a segment -48 on the controller BCyconductcr-IS, contact members 50 on the relay PR, conductor 5|, an interlock 52 on the switch RI, conductor 53 and the actuating coil of the switch FI to negative. The energizing circuit for the switch F2 extends from the conductor 46 through an interlock 54 on the switch R2, conductor 55 and the actuating coil of the switch F2 to negative.

The closing oi the switches LS, FI and F2 connects the traction motor TM across the power conductors l2 and l5 in series-circuit relation with the resistor R. The air engine 22 may be operated to shunt the resistor R from the motor circuit step-by-step by actuating the controller MC to positi'ons'v and 3.

`When the controller MC is in position 2, the magnet valve SV is energized through a circuit which extends :from the conductor 45 through an interlock 55 on the switch FI, conductor 51, a segment 58 on the controller MC, conductor 59, a segment tl on the controller CC, conductor 62, the coil 'of the magnet valve SV, conductor 63 and an interlock 6l on the line switch LS to negative. The magnet valve IV is also energized at this time through a circuit which extends from the conductor 5e through the segment 5l on the controller CC, conductor 65, the Contact members of the relay LR, conductor 66, the actuating coil of the magnet valve IV, conductor B3 and the interlock E4 to negative.

As explained hereinbefore, the operation of the air engine 22 is under the control of the limit relay LR. Thus, when the motor current exceeds a predetermined amount, the contact members of the relay LR are opened to deenergize the magnet valve IV, thereby stopping the progression of the controller CC. The Voperator of the vehicle may also stop the progression of the controller CC by holding the controller MC in position 2, thereby, stopping the controller CC vat a certain point in its travel. The operation of the controller CC maybe resumed by actuating the controller MC to position 3.

If it is desired to decelerate the vehicle, the controller MC is actuated to the ofi position, and the controller BC is actuated to one of the braking positions. When the controller MC is returned to the off position, the switches LS and FI are opened to disconnect the motor from the power circuit. Also the magnet valves of the air engine 22 are deenergized, thereby causing the controller CC to be returned to position l When the controller BC is actuated to position I, the switches B, E and Rl are closed to establish a dynamic braking circuit for the motor TM. The venergizing `circuit for the switch B may be traced from positive through the segment 3| on the switch CS, conductor 32, a segment f'l on the controller BC, conductor lill, an interlock G9 on the switch LS, conductor A"H, the actuating coil of the switch B, conductor ".'2 and contact mernocis c2 and 133 on 'the controller CC to negative. A holding circuit for the switch B is established through an interlock T3 on the switch B.

`Theenergizing circuit for the switch E extends from the Aconductor 'H through the coil -of the switch E, a contact segment Hl on the controller BC, conductor 'l5 and the segment 43 on the controller CC to negative. The energizing -circuit for the switch Rl extends from positive through a segment 16 on the switch CS, conductor '77, a segment 'i8 on the controller BC, vconductor 79, an interlock '8| on the switch Fl, conductor v82 and the actuating coil of the switch RI to negative.

As shown in Figs. 1 and 2, the closing of the switches B and RI establishes a dynamic braking circuit for the motor TM through the resistors R and I9. 'I'his dynamic braking circuit includes the series field winding II and both sections of the series coil 23 of the relay LR. The field winding II is also connected across the power conductors I2 and I5 through the switches E and F2, thereby separately exciting the field winding II and ensuring a prompt building up of the dynamic braking effect.

At this time, the shunt coil 24 of the limit relay LR is connected across the first two steps of the resistor R through a circuit which. extends from one terminal of the resistor section RII through conductor 83, contact members I and 9 of the controller CC, conductor 84, the interlock 26 on the switch LS, conductor 85, the resistor 25, the shunt coil 24, conductor 86, the contact members 21 on the controller CC and conductor 81 to the one terminal of the resistor section RZI. k Thus, the shunt coil 24 is responsive to the voltage-drop across the resistors RII and R2I. 'Ihe coil 24 is so disposed on the relay LR that it aids the series coil 23, thereby lowering the current setting of the relay which causes the relay to operate at a lower current value. In this manner, the braking current is kept at a low value during the first few steps of braking while the vehicle is operating at a high speed. The reduced armature current reduces the excitation of the motor, which is functioning as a generator, thereby keeping its voltage below the maximum permissible voltage. The controller CC is operated in a manner similar to that during acceleration to shunt the resistor R from the motor circuit step-by-step during dynamic braking. The operationiof the controller CC is under the control of the limit relay LR which functions to prevent the motor current from increasingr beyond the setting of the relay. Thus, while the vehicle is operating at a high speed, the resistor sections RII and RZI are kept in the motor circuit to prevent an excessive amount of current from flowing.

After the resistor sections RII and R2I are shunted from the circuit, the shunt coil 24 is no longer effective and the setting of the relay LR is increased toV the normal setting suitable for roperation at moderate speeds of the vehicle. The controller CC is advanced in the usual manner to continue the shunting of the resistor R from the motor circuit.

As explained hereinbefore, the relay PR functions to out off power from the motor TM and automatically establishes the dynamic braking circuits for the motor in the event that the pressure in the air supply system falls below a predetermined amount. 'I'he power is cut olf and dynamic braking is established even though the operator retains the controller MC in a power position and does not operate the braking controller BC. In this manner, the vehicle is kept under control and the operator enabled to stop the vehicle prior to the complete loss of air from the air supply system.

As indicated by the sequence chart in Fig. 5, when the air pressure drops, the contact members and 50 of the relay PR are opened, thereby deenergizing the line switch LS and the reversing switch FI. The opening of the switch FI opens the interlock 56 to deenergize both magnet valves SV and IV, thereby causing the controller CC to be returned to position I.

The piston 28 of the relay PR continues to travel downwardly, thereby closing contact members of the relay PR, which cause the switches B and RI to be closed to establish the dynamic braking circuits and the switch E to be closed to energize the field winding of the motor, as hereinbefore described. The switch F2 remains closed since it is assumed that the vehicle is operating in a forward direction. The switch B is closed by the closing of contact members 88 of the relay PR which are connected in parallel-circuit relation to the contact members bridged by the segments 61 of the controller BC. The switch RI is closed by contact members 89 of the relay PR, which are connected in parallel-circuit relation to the contact members bridged by the segment 18 of the controller BC. The switch E is closed by contact members 9|) of the relay PR which are connected in parallel-circuit relation to the contact members bridged by the segment 14 of the controller BC.

Following the closing of the switch RI, the magnet valves SV and IV are energized to advance the controller CC, thereby shunting the resistor R from the motor circuit in the manner hereinbefore described. The controller CC is advanced regardless of the positions of controllers MC and BC. The energizing circuits for the magnet valves SV and IV extend from the conductor 46 through an interlock 9| on the switch RI, conductor 92, contact members 93 on the relay PR, which parallel the contact members bridged by a segment 94 of the controller BC, conductor 59, and thence through the actuating coils of the magnet valves SV and IV through circuits previously traced. Contact members 95 of the relay PR parallel contact members bridged by a segment 95 on the controller BC, thereby energizing a conductor 91 to keep the magnet valves energized through a segment 98 on the controller CC after the controller has moved past the first few positions.

As explained hereinbefore, a signalling device A is energized through contact members 99 of the relay PR when the pressure in the air supply system drops. In this manner, the operator of the vehicle is notified of the trouble in the air supply system.

From the foregoing description, it is apparent that I have provided a control system which will automatically out ofi power from the propelling motor of a vehicle and establish dynamic braking circuits for the motor when the pressure in the air supply system for the vehicle drops below a predetermined amount. In this manner, the

vehicle is kept under control at all times, and the operator is enabled to stop the Vehicle before the complete loss of the air pressure. The present system greatly increases the safety of vehicles, such as trolley coaches, since loss of control of the vehicle by failure of the air supply system is prevented.

Since numerous changes may be made in the above-described construction, and different embodiments of the invention may be made without 85 departing from the spirit and scope thereof, it is I6 connections including a circuit for separately exciting the motor `field winding; fluidpressure actuated means for causing the operation -of said switching means to establish said dynamic braly ing lconnections when the fluid pressure drcps bclow a predetermined amount, signalling in controlled by said fluid-pressure actuated means, control means controlled :by said fluid-pressure actuated means for disconnecting the separate excitation circuit .alter the Vdynamic braking connections have been established, and relay means responsive to the dynamicbraking current ior also controlling the Yoperation cf said control means.

2. In a control system vfor sa motor having an armature winding land a series field winding, in combination, switching means for establishing dynamic braking connections for the motor, said connections including a circuit for separately exciting the motor eld winding, a controller for normally controlling the-operation of said switching means, fluid-pressure actuated means for causing the operation of said switching means independently of said controller to establish said dynamic braking .connections lwhen the fluid 'pressure drops below a `predetermined amount, control means controlled Iby said huid-pressure actuated means :for controlling the dynamic lbraking current, ,and relay means responsive to the .dynamic braking current for also controlling the operation .of said ycontrol means.

3. 'In a control system yfor a motor having an armature winding and a 'series eld winding, in combination, switclfiing 'means vior establishing dynamic braking connections for the motor, said connections including a circuit for separately exciting the motor "eld winding, a controller for normally .controlling the operation of said switching means, fluid-pressure actuated means for -causing the operation of said switching means independently of said controller to establish said dynamic :braking connections when the Yfluid pressure drops below a predetermined amount, signalling means controlled by ysaid vduid-pressure actuated means, control means controlled by said Huid-pressure actuated means for .controlling the .dynamic braking current, and relay means responsive to the dynamic 'braking current for also controlling the operation of said control means.

4. In a control system for a motor having an armature winding and a series field winding, in combinatioma power conductor, switching means `8 for connecting .the motor to the power conductor, additional switching means for establishing dynamic braking connections for the motor, said connections including a circuit for energizing the motor field Winding from the power conductor, a huid-pressure relay responsive to a predetermined drop in fluid pressure for controlling the operation of said switching means todisconnect the motor armature winding from the power conductor and establish said dynamic braking connections, control means controlled by said relay for opening the circuit for Ienergizing the motor eld winding from the power conductor after the dynamic braking connections have been established, and relay means responsive to the dynamic braking current for also controlling the operation of said control means.

5. In a control system for a motor having an armature winding and a series eld winding, in combination, a power conductor, switching means for connecting the motor to the power conductor, additional switching means for establishing dynamic braking connections for the motor, said connections including a circuit for separately exciting the motor iield winding, a manually opera.- ble controller for normally controlling the -operation of said switching means, Huid-pressure actuated means for causing the operation -of said switching means independently of said controller to disconnect the motor from the power conductor and establish said dynamic braking connections when the fluid pressure drops below a predetermined amount, control means controlled by said fluid-pressure actuated means for controlling the dynamic braking current, and relay means responsive to the dynamic braking current for also controlling the operation of said control means.

EDWARD B. FITZGERALD.

'REFERENCES CITED The following references are of record in the file/of this patent:

4UNIIED STATES PATENTS Number Name Date 765,460 Cutler July 19, 1904 876,594 Schley Jan. 14, 1908 1,081,550 Myers Dec. 16, 1913 1,264,299 Hellmund Apr. 30, 1918 

